Mirror and flip

Two ways to use one side of the character to pose the other. Both are AM_Rig items in the list, both work on all selected controls, and each is a single undo step.

Item	Does
Mirror	Copies the selected control's pose onto its opposite: pose the left hand, mirror, and the right hand matches.
Mirror all below	The same for the control and every control below it — a whole arm, fingers included.
Flip	Swaps the pose of the two sides: the left gets the right's pose and the right gets the left's.
Flip all below	The same for the control and every control below it.

How it finds the other side

For each control it looks for its opposite by name, swapping the side label — L_hand_ctl ↔ R_hand_ctl, arm_L_ctl ↔ arm_R_ctl. A rig that labels sides differently can say so on the control itself, in a side_meta attribute (see Making a rig work with it).

A control with no side — the spine, the head — mirrors onto itself, which leaves it where it is.

What is copied

Translate, rotate and scale, with the sign of each channel flipped where the rig says the two sides point opposite ways (an invTx, invRy… attribute on the control). Locked channels are skipped.

Posing symmetrically

Block the pose on one side, select that side's controls — or just the top one — and Mirror all below. Then break the symmetry by hand; a perfectly mirrored pose rarely looks alive.